Electron multiplier



W. FLECHSIG Oct. 1, 1940.

ELECTRON MULTIPLIER Filed May 3, 1958 Patented Oct. 1, 1940 UNITEDSTATES 2,216,267 ELECTRON MULTIPIJER Werner Flechsig, many, assignorBerlin-Charlottenburg, Gerto the firm Fernseh Aktien- Gesellschaft,Zehlendorf, near Berlin, Germany Application May 3, 1938, Serial No.205,842 In Germany May 3, 1937 4 Claims. (011250-175) This inventionrelates to electron multipliers in which an alternating current isamplified by means of secondary emission, and'particularly it relates tosuch electron multipliers which consist of a series of foraminatedelectrodes held at increasing direct-current potentials whereby primaryelectrons impact one side of the electrodes and are drawn to the otherside.

Such electron multipliers are known in the art,

and it is the object of this invention to overcome wholly or in partcertain defects inherent in constructions known so far. These defectsand means for overcoming the same shall be described in detail in thefollowing:

Referring to the drawing, Fig. 1 is a longitudinal sectional View of anelectron multiplier of the type described in which an embodiment of thepresent invention is incorporated. Fig. 2 is also a longitudinalsectional view of a multiplier in which an embodiment of the presentinvention is incorporated.

Multipliers of the type mentioned, consisting of a series of foraminatedsecondary-emitting electrodes, such as, for instance, wire-mesh grids,

possess the advantage over other multiplier structures that specialmeans for concentration .of the electron stream between two emittingelectrodes is not required. The vast majority of electrons travel alongthe desired predetermined paths be- 30 tween respective electrons.

However, it has been found that the few stray electrons not travelingalong the desired paths can cause disturbances also in this type ofmultiplier, these disturbances resulting in non-uniform 35 amplificationand corresponding distortion of the output current. These strayelectrons can, for

instance, impact the glass wall of the vacuum receptacle and produceundesired charges thereupon. Furthermore, individual stray electronsmay, in this manner, travel along paths avoiding the influence of thecontrol electrode, and also missing the secondary-emitting electrodes.

Furthermore, phenomena were observed in a tube in which the emissionproduced by an indirectly heated cathode was controlled by a controlgrid and then multiplied, these phenomena being explained only by thepresence of ions in the tube.

These ions penetrated into that portion of the vacuum receptacle inwhich the control of the emission takes place and caused considerablefield distortions in that space or caused liberation of secondaryelectrons.

This invention provides for means to prevent the flow of such ions intothe control-grid space,

55 and to prevent simultaneously other disturbances sired paths.

caused by stray electrons traveling along unde- To this end, theinvention provides for dividing the interiorof the vacuum receptacleinto several chambers partially separated from each other by means to bedescribed below. As 5 it is necessary toblock the path for carriers ofnegative as well as of positive charges, an electrostatic blockingpotential cannot be used. The separation of the above-mentioned chambersmust, therefore, be mechanical. In practice, a 10 wall consisting ofinsulating material will be used to separate the individual chambersfrom each other, this wall possessing an aperture covered by aforaminated secondary-emitting electrode, by means of which the electronstream is allowed to 15 pass from one chamber to the other. Ions as wellas electrons can then pass only through the foraminations of theseelectrodes from one chamher into another, all other paths being blocked.The first foraminated electrode following the con- 20 trol grid can thenbe used as an ion collector.

In Fig. 1, a tube is shown which is divided in the above-describedmanner into two chambers. The control of the emission takes place in onechamber, while amplification by secondary emission takes place in theother. The tube l includes an indirectly heated cathode 2, and a controlgrid 3. Secondary-emitting grids 4 are located in the chamber separatedfrom the control-grid space by glass ring 5, which is fused to the Wallof the vacuum receptacle.

In the tube shown in Fig. 2, two separating walls are provided. At oneend is a photoelectric cathode 2 upon which a light beam of undulatingintensity may be incident. Two glass rings 5 are fused to the wall ofthe vacuum receptacle l. The ring closer to the anode possesses agreater inner diameter than that on the side of the cathode, in order toleave suflicient space for introducing electrodes in the construction ofthe tube.

Of course, various other embodiments of the invention are possible; inparticular, the separating wall can be constructed in various ways.Finally, it is also possible to allow certain or all secondary-emittingelectrodes to extend to the walls of the vacuum receptacle and intoclose contact along the entire periphery of each electrode so that thereis no longer a free space between electrode and glass wall through whichions or electrons may travel. It is important only that electrons andions can travel from one chamber to another only through theforaminations in the emitting electrodes because all other paths,particularly that along the walls of the tube, are blocked.

The described division of the vacuum receptacle may also be applied toother types of electron multipliers. It is also within the scope of thisinvention to provide a separating wall in the manner described betweeneach two stages so that each individual chamber contains only oneemitting electrode.

Having thus described my invention, I claim:

1. Electron multiplier, comprising a vacuum receptacle, an electronsource, a plurality of foraminated secondary emissive electrodessupported transversely of said receptacle with their edges in spacedrelationship to the Wall of said receptacle, and a collector electrode,said vacuum receptacle having a partition of insulating ma,- terialbetween said source of electrons and said secondary emissive electrodesandextending inwardly from the wall of said receptacle a distance atleast equal to the space separation of the edges of said electrodes fromsaid Wall.

2 Electron multiplier, comprising a vacuum receptacle of glass, anelectron source, means for control of the emission from said electronsource, a plurality of foraminated secondary emissive electrodessupported transversely of said receptacle with an edge thereof in spacedrelationship to the wall of said receptacle, and a collector electrode,said glass receptacle having a partition of glass extending inwardlyfrom said wall to a distance at least equal to the space separation ofsaid edge from said wall and located between said source and saidsecondary emissive elec trodes.

3. An electron discharge device comprising an envelope, a cathode, anelectron multiplier grid, a collector electrode, said grid beingpositioned between said cathode and said collector electrode with theedges of said grid in spaced relation to the inner Walls of saidenvelope, and a ring of insulating material extending inwardly from theinner Walls of said envelope past the outer edgesof said grid andforming with said grid a partition dividing said envelope into twochambers, one chamber containing said cathode and one containing saidcollector electrode.

4. An electron discharge device comprising an envelope, a cathode, a.plurality of electron multiplier grids, a collector electrode, saidgrids being positioned between said cathode and said collector electrodewith the, edges of each grid in spaced relation to the inner wallsplurality of rings of insulating material extending inwardly from theinner walls of said envelope past the outer edges of respective ones ofsaid grids and forming with said grids partitions dividing the interiorof said envelope into a plurality of chambers, one of said chamberscontaining said cathode and another of said chambers containing saidcollector electrode.

WERNER FLECHSIG.

of said envelope, and a I

